The Study On Mandibular Movement Before And After Treatment For Tooth Wear

[Objective]The aim of this study was to explore the effect of mandibular movement, chewing EMG amplitude and condylar position before and after treatment for tooth wear.[Materials and Methods] 10 patients with severe tooth wear need to transitional occlusal rehabilitation were selected and divided into two groups:Group I with both side posterior support lost (5 cases) and groupâ…¡with complete posterior tooth support (5 cases).10 normal dentition healthy volunteers were also selected as control group. Using the SAM axioquick recorder and surface electromyography (EMG) record the incisor points mandibular trace and range of groupâ… , groupâ…¡'s knock teeth movement, edge movement, chewing movement before and after 1 month transitional restoration. Testing the center of condyle trajectory features on the coronal, sagittal, horizontal plane and recording protrusion condylar slope, non-working side lateral condylar slope and simultaneous EMG amplitude, Through Xu Le-bit chip testing condylar the space before and after the transition restoration; Group I and Group II compared using a paired t test before and 1 month after transition; group I, group II and contral group compared using single factor analysis (ANOVA), P<0.05, the differences were significant.[Results] 1. The trajectory repeatability of control group's mandibular incisor point movement as follows:knock-tooth movement> protrusive movement> left and right lateral movements> maximum opening movement; The maximum open type is Skew,open curve and close curve are common separated in the middle of the movement; Left and right side trajectory with good symmetry, the range of motion was difference but no significant (P> 0.05); Chewing ring is smooth, out and in curve is regularity; Condylar center trajectory is smooth, left and right curve is good symmetry, non-working side condyle slope is greater than the protrusive condylar slope on sagittal plane. The normal control group's edge movement and masseter movement's mastication EMG magnitude are larger than the temporal; The Xu Le-bit chip shows condylar position in the center of joints, front, back and up joint space are normal.2. Group I,Before and after trasition restore the mandibular incisor point knock-teeth movement repeatability is good; The trajectory of mandibular incisor point edge movement is not smooth, irregular, showing a high degree of asymmetry, Mandibular movement index is low; After 1 month transitional restore, The trajectory of mandibular incisor point edge movement's smoothness,regularity,symmetry is improved,Mandibular movement index is increased (P<0.05); The mandibular incisor point maximum opening movement's range is increased than before restoration on coronal and sagittal plane on frontal plane (P<0.05); Protrusive movement's range is lower than before restoration (P<0.05); Left and right side's range of movement are increased than before restoration (P<0.05); Before transition restoration chewing movement is disorder, the range of movement is small, After transition the trajectory is improved, the increased range of movment was significantly (P<0.05); After transitional rehabilitation the condylar center trajectory is significant improvement in morphology, showing more fluency and goodness.Before transition restore non-working side condyle slope is less than protrusive condylar slope on the sagittal plane, Bennett angle is much higher than the normal control group, the different was significan (P<0.01). After transitionr restore bennett angle is reduced than before restoration but higher than the normal control group (P<0.05).3. Groupâ…¡, The knock movement's and edge movement's trajectory repeat is good.The mandibular index is significantly higher than the group I (P<0.05), After transitional restore mandibular index is increased,compared the control group, the difference is no significant (P> 0.05); Group II, The range of maximum movement was no significant difference between the former and after transitional restore (P> 0.05),Protrusive movement trajectory range is decreased than before transition restore on the frontal (P<0.05),The range of left and right side trajectory is increases than before restoration (P<0.01); Chewing ring is diverse and multi-loop forms is irregular, After transitional the range of chewing ring was significantly increased (P<0.05); The trajectory's morphology of condyle center did not significantly change before and after restore, Before transition restoration non-working side condyle slope is less than the protrusive condylar slope on sagittal plane Bennett angle is much higher than the normal control group,the differences was significant (P<0.05). After transition bennett angle is reduced than before.Compared with the control group the difference was no significant (P>0.05).4. Group I groupâ…¡mandibular edge movement the temporalis muscle EMG amplitude was significantly higher than the control group, the masseter muscle EMG is lower rate during mastication, After transitional rehabilitation, the mandibular edge movement masseter muscle EMG amplitude increased. The temporal muscle power decreased, Masseter muscle EMG increase over the transition during mastication.5.X films showed that the groupâ… , groupâ…¡condyle position shift after, the gap of before is widen,after space is narrow, After transitional before qap of condyle is smaller than before and after gap more widen(P<0.05)[Conclusion] 1. The regularity of normal mandibular movement is good, Open-type exists skew.The range of left and right lateral movements is no difference. Non-working side of condylar slope is greater than the protrusive condylar slope on sagittal plane, The masseter muscle power range of mandibular edge movement was larger than the temporal's range.2. The height of tooth wear occlusion increased only in the rest gap is not easy evoked TMJ symptoms, After 1 month transitional rehabilitation can adapt to the new height.3.The trajectory of mandibular movement can provid help to diagnosis TMD. After transitional restore,mandibular trajectory's shape was significantly improved, Mandibular movement index increased.4. The mandibular movement of severe tooth wear is limit before restoration, indicating that the transition restore is an effective way to improve mandibular movement.5. Before restoration The trajectory of condylar center is not smooth, indicating that may be barriers to joint movement, After transition the trajectory is significant improvement. This study found that condylar protrusive condylar slope is larger than non-working side of the condyle slope, indicating that most patients with severe wear may exist movement dysfunction.6. When mandibular is edge movement,the EMG amplitude of tooth wear is too high, May be one of the reason that lead severe wear, Transitional rehabilitation can restore normal chewing EMG amplitude.7. The mandibular condyle position is shift after, the former of joint space become larger, the after gap become smaller, After trasition restore can make before of joint space become Small, the after gap increase and make condyle in the middle of concave.